SpudFiles

I have chosen 15mm copper pipe for barrel, length is undecided as yet and 7/32 brass for breach its an airtight fit slides smoothly in barrel too, im assuming i need 3-way valve, im using piston with return spring to move either barrel over breech or reverse which ever works best with flow of things, am not after mega rof just smooth operation a reg is needed because cannister is an ex fire extinguisher its rated to 300psi dont think im going that high ill end up firin confetti, once i know whats going inside will post pics of progress just need a foot up on the air side of things, i want it to be safe as im sure my son wants to pezzle me with flying foam, after understanding comp air ive got plans to do spudgun

Any help appreciated

Holy run-on sentence batman!

Some pictures of what you have/are planning would be easier to comprehend.

Regarding semi-auto, I recommend cheap eBay parts have a look here:

http://www.spudfiles.com/forums/semi-au ... 23626.html

If you want it for nerf darts, you really don't need that much pressure, so a pressure regulator between tank and three way is definitely a good idea, I would think that you could get by with 20-30 psi in your firing chamber.